A barrier blocks the Washington Monument during the October 2013 government shutdown. (Mike Theiler/Reuters)

The last government shutdown, almost a year ago, was no fun for anyone. Republicans in the House and Senate demanded that legislation to fund the government simultaneously defund Obamacare; Democrats refused to go along. In the ensuing 16-day stalemate, many functions of the federal government were forced to shutter. Federal workers were furloughed or worked without pay, children were disenrolled from Head Start, and the U.S. economy lost about $24 billion. Heartbreakingly, the annual Assateague Pony Roundup was canceled. Veterans were forced to commit civil disobedience and break into national monuments. (Okay, the shutdown was apparently fun for a few people: Nine months later, there were anecdotal reports of a D.C.-area baby boom.)

The shutdown was particularly hard on Republicans' image, as voters primarily blamed them for the chaos. Once it was over, the GOP seemed to have learned its lesson about the price of obstinacy. In December, Democrats and Republicans in the House and Senate negotiated a budget deal setting spending levels through 2015, and in January both houses easily approved the funding for it—the first time since 2009 Congress had passed a real budget rather than a temporary spending authorization known as a continuing resolution. A new era of rationality and calm seemed to have dawned.

But while the topline budget numbers set by the budget deal go through October 2015, the funding passed in January expires at the end of next month, on September 30. Both houses must pass new funding bills—likely in the form of a continuing resolution—to keep the government running. And that has raised the possibility of further shenanigans.

A well-placed House Republican source tells me GOP leadership is increasingly nervous about the potential for a rebellion on the funding bill. The small but influential hard core of House conservatives were emboldened by what happened earlier this month with the border bill: A proposal favored by Speaker John Boehner to address the border crisis with emergency funding and expedited deportations had to be pulled when conservatives, egged on by Senator Ted Cruz, revolted. The legislation the House passed instead had a smaller price tag and would bar President Obama from continuing his policy of allowing some young undocumented immigrants to stay in the U.S. The Democrat-led Senate, meanwhile, did not manage to pass its own version of border legislation at all, so Congress failed to act on the issue.

Republican leaders are worried that conservatives will not go along with a simple government-funding bill unless it reflects their priorities.

House conservatives like Michele Bachmann and Steve King considered the episode a major victory. Bachmann called it a highlight of her career. Now, Republican leaders are worried that conservatives will not go along with a simple government-funding bill unless it reflects their priorities.

One possibility, raised by Senator Marco Rubio in an interview with Breitbart this week, is attaching to the funding bill a mechanism to stop Obama from taking executive action to liberalize immigration enforcement, as he has already done and threatens to do further. "There will have to be some sort of a budget vote or a continuing-resolution vote, so I assume there will be some sort of a vote on this," he told the publication. "I'm interested to see what kinds of ideas my colleagues have about using funding mechanisms to address this issue." Making government funding contingent on immigration-related legislation would instantly turn it into a highly charged partisan battle.

Another possibility is that reauthorization of the Export-Import Bank would be attached to the continuing resolution, either by Senate Democrats or by House Republican leadership. The formerly obscure lending fund has drawn the ire of the grassroots left and right, but mostly right, which charges that it constitutes a cronyistic corporate-welfare scheme. The bank's authorization runs out on September 30, the same day the federal government funding is set to expire. Business groups are lobbying hard for its renewal, but opposition has now gained momentum among conservatives: At this month's meeting of the Republican National Committee, a resolution opposing the bank was only narrowly defeated by the committee's members, 67 votes to 63. House conservatives might well refuse to agree to a government-funding bill that also reauthorizes the bank.

(Some recent coverage has also highlighted comments by Senate Minority Leader Mitch McConnell, who told Politico he planned to push through spending bills "with a lot of restrictions on the activities of the bureaucracy." But McConnell was talking about what he would do if Republicans take the Senate next year. He was not referring to next month's legislation, which the pragmatic Kentuckian presumably wants to get passed as smoothly as possible.)

"The last thing we're going to do is shoot ourselves in the foot and jeopardize our chances of winning the Senate and gaining seats in the House."

All this is highly speculative. Officially, Republicans insist there will be no drama, although they aren't yet saying what the plan is for getting the funding bill passed. "The last thing we're going to do is shoot ourselves in the foot and jeopardize our chances of winning the Senate and gaining seats in the House," a senior House GOP aide told me Wednesday. A top Senate Republican staffer agreed when I asked about a possible shutdown: "Absolutely not." Paul Ryan, the chairman of the House Budget Committee (and co-author of the budget agreement), told Business Insider, "No, there will not be a government shutdown"—although he then added, "If there is a government shutdown, it'll be because the Democrats brought it about."

Indeed, Democrats have ample incentive to stoke talk of a shutdown—or even to provoke one. Since last year's shutdown ended and the Obamacare rollout disaster ensued, their political fortunes have declined. On Wednesday, the Democrats' House campaign arm launched a website to remind the world that, prior to the 2013 shutdown, Republicans swore there was no possibility of such an outcome.

But not all Republicans are convinced the shutdown was such a disaster for them. A few weeks ago in Texas, I watched Cruz tell a roomful of conservative activists that the fight to defund Obamacare was actually a partial victory. "If you listen to Democrats, if you listen to the media—although I repeat myself—they will tell you that fight last summer and fall didn't succeed," he said. But, he asked, "Where are we now today?" The president's approval ratings are lower than ever, voters overwhelmingly dislike Obamacare, and Republicans have a chance at winning a dozen or more Senate seats. Rather than suffer a setback in the shutdown (which he did not mention), Cruz said, "I believe we have laid the foundation for winning the war to repeal Obamacare."

If conservatives buy Cruz's logic, which they tend to do, the prospect of another shutdown might not scare them much. And that could mean Congress is headed for trouble.